3

FIELD TEST

he Circuit Playground Express (CPX) is

a programmable microcontroller board

that makes it really easy to get started.

Plug it into a computer with a micro USB

cable and you’re ready to start coding.

The UF2 firmware takes software into

the board in two ways: either you can press the reset

button to enter programming mode and copy UF2

files into a new drive that will appear on your machine,

or you can upload directly from the Arduino IDE. For

beginners the first method will be easier, as you can

generate these UF2 files from either the web-based

MakeCode block-based editor or from a Circuit Python

development environment.

On some versions of Windows, you’ll need to install

drivers, but on Mac OS X, Linux and Windows 10, you

don’t need to install anything if you use MakeCode – just

plug your board into a USB port, then point your browser

to makecode.adafruit.com to start your first project.

BUILT-IN FEATURES

From here you can take advantage of the wide range of

hardware that’s packed onto the board. For output, there

are ten NeoPixels and a speaker (not just a buzzer).

For input, there are two buttons, a slide switch, an

accelerometer, a temperature sensor, a microphone,

and a light sensor. With all this, you can put together

some pretty fancy projects straight away. For our first

project, we made an indicator for cyclists. It uses the

large holes on the CPX to attach it to the back of a

cycling glove, then uses the accelerometer to recognise

when the hand is held out indicating a turn and flashes

the NeoPixels orange. This took 18 lines of dragged-and-

dropped code in MakeCode and no additional hardware

(most of these were to ensure that there was a stable

reading from the accelerometer). While it’s hardly a

complex project, it shows that you can build useful

projects quickly with no additional hardware or software.

There’s nothing on the Circuit Playground Express

that’s fundamentally unique – you can get the

same sensors and outputs to attach to virtually any

microcontroller. What makes this board special is the

way it’s brought together into a single package. It’s

hard to think of any project where you’ll need all the

features available, but given the £25 price tag, it’s easy

to justify the cost even if you only need one or two of

the extra input or output options. By bringing them all

onto the main board, there’s no extra setup or wiring,

and it’s all supported by the software without having to

add any libraries, which again makes it thankfully easy

to get started.

The one obvious thing missing from the device is

any form of networking. It does have a built-in infra-red

receiver and transmitter, I2C and UART, but no WiFi

or Bluetooth. The other major limitation of the board is

that it’s not breadboard-friendly – it’s far more suited to

crocodile clips or banana plugs.

MANY, MANY POSSIBILITIES

Whether or not these are really limitations depends

a lot on the sort of projects you’re working on. The

CPX isn’t going to work well for Internet of Things-

type applications. It’s also not going to work well as

a controller for building complex circuits – having just

eight GPIOs limits the amount of hardware you can

connect. Anyway, there are lots of microcontroller

boards far more suited to these uses. However, the

CPX makes it fantastically easy to get started with

embedded and physical computing projects. You can

build on the integrated hardware with the eight GPIOs.

Seven of these can detect capacitive touch input, so

to add more user input to your project, you just need

a few crocodile clips and leads. As all the GPIOs can

read analogue input, it’s also trivial to add input from

and device that gives a varying voltage as it’s output.

There are also five PWM output pins for driving LEDs

at different brightnesses. The MakeCode platform is a

code repository as well as an IDE, and there are a set

of tutorials from Adafruit to help you get started with

the platform and the hardware.

The CPX is well suited to people getting their first

microcontroller, either buying one themselves for fun

or as part of a taught course. For this purpose, it’s

genuinely hard to fault the CPX. It’s easy to learn with

no (or minimal) software to install, yet at the same time

allows you to use more advanced languages if you’ve

got the knowledge and experience. It packs a fantastic

range of input and output options onto the board,

which means that you can dive right into some more

interesting projects without getting immediately bogged

down in attaching extra hardware. It’s also easy to start

to build simple circuits off using crocodile clips.

Perhaps the ultimate test of any bit of hobbyist kit is

whether or not it sparks excitement. For us, the CPX

gave us a childlike sense of glee, because it makes

so much so easy. This is great for beginners and any

hobbyists who like to quickly prototype projects.

FIELD TEST

T

The CPX is well suited to people getting their first

microcontroller, either buying one themselves for

fun or as part of a taught course

”

”

The best

microcontroller

board for

introducing

people to

physical

computing

projects.

10 / 10

VERDICT